Transcript Bacterial Contamination in Ethanol Fermentation

BACTERIAL
CONTAMINATION
IN
ETHANOL
FERMENTATION
KENNETH M. BISCHOFF, SIQING LIU, TIMOTHY D. LEATHERS, RONALD E. WORTHINGTON, JOSEPH O.
RICH.
NATIONAL CENTER FOR AGRICULTURAL UTILIZATION RESEARCH, U.S. DEPA RTMENT OF AGRICULTURE.
PUBLISHED 2008 WILEY PERIODICALS, INC DOI 10.1002/BIT.22244
PRESENTED BY: MOHAMMAD ALI AL-AMEEN
NOVEMBER 29 2012
BIOPROCESSING AND BIOTECHNOLOGY
DR. SONIA M. TIQUIA-ARASHIRO
THE BIG THREE..
What is ethanol?
• Ethanol is a colorless volatile flammable liquid. Ethanol is also
called ethyl alcohol, pure alcohol, grain alcohol, or drinking
alcohol.
How is it produced?
• Fermentation is when certain species of yeast (e.g.,
Saccharomyces cerevisiae) break sugar in reduced-oxygen
conditions to produce ethanol and carbon dioxide.
Why it’s produced?
• It’s the main component of many important commercial
products such as Alcoholic beverages, food, drugs, and also
used as an energetic fuel component.
THE PROBLEM
Bacterial contamination is a critical problem, particularly in fuel ethanol
fermentations that are not performed under sterile, pure-culture
conditions.
• Bacteria would grow on the substrate available for the yeast yielding
competition with yeast and lower production of ethanol.
• Infections could occur and the fermenting facility may result in a “stuck”
fermentation which require a “costly” complete shutdown of the facility.
• The emergence of antibiotic resistant bacteria may limit the
effectiveness of antibiotics to treat bacterial contamination, and
therefore, there need to be a tool that test the development of new
antibacterial agents.
•
This tool should also monitor the growth of contaminants in the medium.
EMERGING
SOLUTIONS?
What criteria are followed in this model?
• Cost-efficiency
• Effective
• Simple
SHAKE FLASK
FERMENTATION
• Bioreactors are good for simulating the industrial fermentation
process, but their high cost in terms of equipment, media
consumption, and labor limit the practical number of combinations of
these variables.
• The author decided to monitor the contamination using a shake-flask
fermentation model challenged with bacterial strains isolated as
contaminants of fuel ethanol facilities.
• Strains of Lactobacillus harvested from ethanol fermentation facilities
will be used as the challenging contaminant.
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PUTTING THE MODEL
INTO EXAMINATION
The goal is to model bacteria growth and reaction to antibiotics.
However, there are variables that needs to be examined including:
• The feedstock
•
YP/glucose and corn mash
• Bacterial Strain
•
Six lactic acid bacteria
• Bacterial load
•
Amount of bacteria added (testing between 104 CFU/ml to 108 CFU/ml).
• Antibacterial treatment.
•
Treating with Virginiamycin
HPLC ANALYSIS
High performance
liquid
chromatography was
used to determine
the concentrations
ethanol, glucose,
lactic acid, and
acetic acid.
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RESULTS AND
DISCUSSION
THE FEEDSTOCK
Use of glucose in YP media may represent the state of a chronic
bacterial infection, but doesn’t effectively simulate the state of acute
infections.
BACTERIAL STRAIN
L. Fermentum 0315-1, L.fermentum 0315-25 and L.brevis 84 produced the most deleterious effect on
the yeast-catalyzed fermentation
BACTERIAL LOAD
TREATMENT WITH ANTIBIOTIC
L.Fermentum 0315-1 didn’t get affected by Virginiamycin
CONCLUSION
Bacterial contamination in ethanol fermentation is a serious problem that
needs to be monitored. In this article, shake-flask fermentation is used.
Several variables were studied on this model.
• Not enough variables. There are more variables that can be looked at
like Nitrogen and Potassium in the media which might cause
fermentation to stop if not present in a good amount
• Is this model better than Bioreactor monitoring?
•
•
•
They used HPLC which can be substituted by the bioreactor itself
monitoring the growth and concentration itself.
How does this model work on sterile, pure culture conditions. Is it more
accurate than the bioreactor?
Industry can afford a bioreactor.
REFERENCES
• Partitioning of Potassium during Commercial-Scale Red
Wine Fermentations and Model Wine Extractions
Am. J. Enol. Vitic. March 1, 2009 60:43-49
• Influence of Medium Buffering Capacity on Inhibition of
Saccharomyces cerevisiae Growth by Acetic and Lactic
Acids
Appl. Environ. Microbiol. April 1, 2002 68:1616-162
• Effect of yeast inoculation rate on the metabolism of
contaminating lactobacilli during fermentation of corn
mash.
• J Ind Microbiol Biotechnol. 2004 Dec;31(12):581-4. Epub
2004 Dec 14
Q&A